Data networks that utilize an IETF communication protocol standard include a plurality of routers that are interoperably coupled to each other and to network segments. Host devices, such as personal computers, video telephones, telephones, facsimile machines, etc., are coupled to the network segments and transfer data to each other via the routers. In order to support such data transportation, the routers communicate with each other using routing protocols to obtain routes between the various network segments and corresponding hosts of the segments. Standard bodies, such as IETF, ATM forum, etc., have standardized various routing protocols.
To further support the data transportation, routers include one or more route computation engines and one or more forwarding engines. The route computation engine executes the routing protocols and generates forwarding tables. (Note that a forwarding table is often referred to as forwarding information base (FIB).) The forwarding engines forward packets from one network segment to another based on forwarding information contained in the forwarding tables. In legacy routers (i.e., routers that have been installed in data networks for some time), the software and hardware of the routing engine and of the forwarding engines are contained within the same physical structure. As such, the interaction and control of data transportations between the routing engine and forwarding engines was trivial.
To provide distributed routing functions, distributed routers have been developed in which the various components of the router (e.g., the route computation engine and forwarding engines) are logically separate entities that may be contained within physically diverse packages. In prior art systems, communication between the components of a distributed router is based on a query response model. In such a model, the forwarding engine sends a query to the route computation engine whenever it needs forwarding information. On receipt of the query, the routing engine, or route computing component, accesses its forwarding tables, or other local databases, and responds with the appropriate information. A query response is exchanged for each element of forwarding information required. In a large network, with multiple accessible networks and hosts, a substantial amount of communication between the forwarding engines and the route computation engine is required just to handle the query response mechanism. In other words, each time a forwarding engine has a data packet to transmit, it must query the routing engine to obtain forwarding information. As the size of the network increases, the amount of control traffic required to process the queries increases correspondingly.
Therefore, a need exists for a method and apparatus that reduces overhead traffic in providing routing information for forwarding packets within a distributed router.